Radio Frequency (RF) communications between nodes of a network typically require a carrier wave to be used to transport data signals from one node to the next. However, nodes of a network may not be frequency agile so that multiple nodes must communicate using the same carrier frequency. This may be especially true for wireless networks of medical devices where the availability of radio frequency spectrum is limited due to technological and regulatory reasons. The lack of frequency agility may be necessary to maintain communications within an allotted spectrum and/or to reduce the complexity and cost of the transceivers of the network nodes.
For communications between many nodes to occur through using the same carrier, collisions of the communications must be avoided. Collisions occur where two or more nodes attempt to transmit at the same time on the same carrier so that a receiving node is exposed to multiple transmissions simultaneously. The multiple transmissions cannot be individually decoded at the receiving node because they interfere with one another. Thus, to prevent collisions, the multiple nodes within range of one another who utilize the same carrier must operate so that only a single node transmits on the carrier at a given time.
To synchronize transmissions, nodes must not simply transmit at any time when a transmission may be desired. The nodes must have some ability to determine when another node is about to transmit on the carrier to avoid transmitting at the same time. This synchronization of transmissions is further complicated when nodes come and go within a network, which is typical within a wireless network, and when transmissions between nodes have varying degrees of urgency.